Nowadays, meals served outside the home, i.e. in canteens, clinics, care establishments etc., may be delivered and prepared in two ways. The meals are prepared either by an outside or an inside catering service.
The meals may be delivered to the place of consumption in two different states: i.e. cold followed by reheating either by induction or conduction--forced air--microwave--bain marie, or with the contents separate or maintained at temperature, in which case the temperature of the delivery may amount to +4 degrees C. or -2 degrees C.; or delivered hot on an insulated tray.
In the case of cold food distribution, the meals are prepared and presented on trays in a transport trolley which may also serve as a reheating trolley. This trolley is then transported in a refrigerated condition to the place of consumption where the meals are reheated.
In the case of hot food distribution, the meals are prepared and presented on trays, which may either be insulated (to keep hot and cold for an hour and a half) or a standard tray used in conjunction with insulated products which keep the food at correct temperature for three-quarters of an hour (base and cloche). The trays are then placed in a trolley and delivered as quickly as possible.
In the case of the hot food system using standard trays in conjunction with isothermal products, the meals cannot be prepared long in advance (not more than three-quarters of an hour). The consumption of meals must not be delayed. This system allows flexible presentation of the trays.
In the case of the cold food system to be reheated by induction, the heating is carried out by a hotplate underneath the dish. This method often results in the food at the bottom of the dish being burned and the food above it being poorly reheated. There also has to be holes in the tray, i.e. a special tray is required. Additionally, there must be a special place on the tray for heating a plate and a bowl of soup, which means that trays must be identical. If the reheating trolley is also the transport trolley, this means that it is very heavy, very expensive and very fragile. Special meals (which must remain cold) cannot be placed on the same trolley, as everything will be heated by the hotplates located underneath the dishes. The trolley must be used with care and be well maintained because the heating trolley is also used for transport. This is a very costly system and as many trolleys with hotplates are required as the number of meals served. The heating time varies between 30 and 45 minutes.
In the cold food system the existing heating system by means of induction is fragile as the inductors are located in the transport trolley. A silver disc is fixed to the base of each plate to be reheated. However, this requires two stocks of plates: one for hot dishes and one for cold dishes. There is a hot zone and a cold zone on the trays, and hence no flexibility. This system is expensive because the reheating trolley is also the transport trolley. Handling must be carried out with care because the inductors are frequently touched during handling of the trays. Moreover, the transport trolley is very heavy.